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43l Cobra makes a clunk bang as if we hit something

davidlyne

Member
"Hi all, we have a 4.3l OMC wi

"Hi all, we have a 4.3l OMC with Cobra drive. First off, thanks for your previous help. We went out on Saturday and after leaving the Marina, about 10 minutes at 6 knots, we accelerated up to 22 knots @ approx 3,400RPM. 5 minutes later there was a clunk / bang as if we had hit a small log. All Ok for another 3 or 4 minutes then the same noise again. Still wasn't sure then the noise again. Slowed down to idle and the drive seemed noisier than usual. Kept it at around 1200RPM and motored slowly back to marina. This took about 30 minutes. If I tried to go any faster the noise would be back. At the marina the boat would still go in and out of forward and reverse. Any ideas what could be wrong? With limited mechanical ability is there something simple I should look at or should I just call in the mechanic?"
 
"the clutch dogs in your lower

"the clutch dogs in your lower unit are disengaging. You will need the lower unit rebuilt or replaced. The root cause may be your shift cable(s), so correct that before damaging the next lower or gears.
www.hastings.org/~stuart/cobra"
 
"Hows the oil in the outdrive

"Hows the oil in the outdrive alot of shavings?

If yes gear went, when you take it apart you will find out, if it's the pinion or what.

Did you ever check the out drive oil all summer?

This could have just happened even if you didn't have water in the oil.

When was the drive apart last?

Maybe you could have seen or prevented this from happening.

Maybe bearing?"
 
"HI Guys, Thanks for the respo

"HI Guys, Thanks for the responses. After I got Hy Stat's answer I new it was too big a job for me. I called the mechanic, but due to rain here he hasn't been able to remove the drive yet.

Without seeing the drive he gave me the same diagnosis as Hy Stat. To answer chiefalan, I didn't check anything when we returned on Saturday.

I do check the oil regularly. I had made a previous post on here in regards to possible water in the oil and was due to have that checked / changed. The drive has not been apart since I have owned the boat, which is approx 2 years, but it was removed to replace the gimble bearing and the universal joints around 9 months ago.

Based on what I have been told, my shift was too hard, so I suspect in hindsight, I may have been able to prevent this from happening. I know next time.

I look at it this way, my drive will be fixed, cable will be adjusted correctly / replaced if needed, and I will have a have good reliable boat again.

One question for you guys, as I really like the boat and don't want to sell it, should I get the drive fixed orreplace the complete engine / drive with a used Mercruiser or get a used outboard put on the back mounted on a pod?

cost wise, worst case complete rebuild of drive $2,ooo, I can get a used mercruiser for $8,000 then I need to get transom modified and installed or outboard option will cost around $8,000 installed

What would you guys do / recommend. regards David"
 
"SEI are trying to get a Cobra

"SEI are trying to get a Cobra reproduction drive onto the market for spring 2009.
I would get the analysis and then if you need a drive, sit and wait for a while."
 
"Hi Guys, Just thought I would

"Hi Guys, Just thought I would give you an update. Seems the prop shaft seal let go and I lost all the oil in the drive. There was about 100ml of oil in there instead of the 3 litres or so required. It obviously got hot and stripped gears. My mechanic found me a really good used lower unit and he is going to put new seals etc, pressure test and I am back on the water. Thanks for your replies. David"
 
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